DIY schematics with questions

[fl0w]

I wasn't gonna go down this DIY route but here I am...

I would really appreciate feedback on below schematic, any type of feedback really but mainly regarding safety and whether it even makes sense from a stimming perspective (0 stimming experience).

I've cobbled together a design based on the ones I've come across - TroniC midi/pro and lolo2 mostly and this is what I have.

Screenshot from 2022-12-06 17-15-57.png (73.32 KiB) Viewed 4168 times

1) Trodes OFF aka. kill switch.
Why is the Trodes OFF switch in TroniC Design 2 Pro-Build after the transformer with a 4-pole switch requiring a resistor rather than right after the amp with a dual pole switch?
I've included two possible Trode OFF switches in the schematics, A and B - one will be picked.
Are there any downside to A? Wouldn't turning this switch off in practice be equivalent of having the amp running without anything plugged in?

2) Serial resistors.
a) I've seen mentions of both 3.3 as well as 3.9 Ohms (and other values) for the serial resistors R1, R3. I'm curious of what those values corresponds to in reality, as sensations so I initially thought of buying both and making them selectable through a switch. But later changed them to work in parallel so one is always on and by flicking the switch we include the other - this seems to be what's called a boost in the TroniC design. By my calculations the serial resistance in my design is 3.9 Ohms but becomes 3.3 Ohms when SW1 is on. Does that seem correct?
b) My design switches between 3.9 and 3.3 Ohms but TroniC seems to switch between 4.7 and 3.3. What would you consider when picking this max resistor? I'm leaning towards 3.9 because that's what lolo2s design proposes.

3) Triphase
I initially went with the switch proposed in lolo2s design which simply "connects the blacks" by a switch but then saw the triphase switch in TroniC pro-build. It allows you to switch which pair of wires to connect - so, connect blacks, connect reds or off, I hope you understand what I mean. It seems like a rather simple "upgrade" if one were to implement a triphase switch anyways. But I've not seen this in any other designs, any reason to why? Is this even useful for stimming? I'm guessing yes because it's included in the "pro"-build but surprised by the lack of it in other designs despite it being such a simple upgrade.

4) Invert channel
I'm thinking of adding a switch to invert a channel, i.e. exchange output of Y1 and Y2 and the same for Y3 and Y4 would this be useful in anyway for stimming? Dangerous?

[edger477]

I only built like 3 or 4 boxes so I do not have 1st hand experience with all of the questions but I will try to start answering them.

1) Because the transformers are consuming signal on one side and inducing it on other... if you cut of signal suddenly that change might also result in big change on output. I did not have this switch in any of my boxes as I was careful with input volumes etc so did not got into situation where I needed it, but is definitely nice safety feature.
EDIT: if you have a good amp that shuts down and turns on without a "pop" - which you should, then you can use its power switch as master kill switch.
2) Those additional resistors (3.3 sounds right, it is r1xr2/(r1+r2) if I remember from college give you a "boost" but nothing you cannot accomplish through volume control. Could be fun if instead of switch is controlled by a relay and a program (arduino/esp etc)... i.e. if you are into self-bondage and you need to get out early but you don't want to use emergency button, you could have alternate one that activates boost and then lets you out in a minute or so...
3) I have this one, and it is useful because triphase signals feel different depending on what is common and what is configuration.
I also have 2 switches to change polarity of each channel (again mostly for triphase, to change which end is common)

4) I do not have this one, but is a nice feature, it saves you time for swapping cables from a to be and vice versa. You can easily get it with Voicemeeter, there is button to loop through normal/mono/inverted for each output.

[fl0w]

Thank you very much for your input in this @edger477. I have a question for you since you've mentioned in another thread that you have several amps - do you have a recommendation for a 2ch amp with individual volume controls? I'm only finding ones with a single master vol control. Either I'll go with a recommended Breezer TPA3116 (even though it only has a single vol control and I guess I'll have to adjust left/right straight from the source, even if it feels cumbersome... Although I've read recommendations to do it anyways, i.e. don't use vol controls of the amp - why's that?) or I might go with the one you mentioned here, 4ch BT amp with 4 vol controls, although I won't be using the extra 2 channels... Bur preferrable I'd like to find a 2ch 2 vol controls amp.

For reference I've updated the schematics with inversion and individual channel off switches as well as an All-trodes-OFF switch.

Screenshot_20221208_115638.png (23.44 KiB) Viewed 3097 times

Also, since the forum I see mentioned the most, smartstim, is gone, where do people gather nowadays to talk DIY etc?

[edger477]

For amp I use this

https://www.amazon.de/-/en/gp/product/B087FWWVB6

You have 2 extra channels, but you can easily build another midstim for them :)

Also, for DIY, you should check this viewtopic.php?t=23302&start=240

Not aware of other forums.

[JakofClubs]

To use the top channel as an example, I don't think you want to add R5 in parallel with R1. R1 sets the minimum impedance the amp sees to 3.9 ohms. Most amps don't like a lower impedance than about 4 ohms. Any resistor you add in parallel to R1 will lower the overall impedance. Your example effective lowers the impedance to 3.3 ohms.

I would recommend a high-pass filter (blocks low frequencies) with a 35v (minimum) bi-polar capacitor between 100uf and 330uf. These are the values I've tried, Others could work. I added these capacitors and it felt a lot better for pleasure. It goes before the transformer. You could add a SPST toggle switch that bypasses the capacitor by bridging around it if you want more pain.

[fl0w]

To use the top channel as an example, I don't think you want to add R5 in parallel with R1. R1 sets the minimum impedance the amp sees to 3.9 ohms. Most amps don't like a lower impedance than about 4 ohms. Any resistor you add in parallel to R1 will lower the overall impedance. Your example effective lowers the impedance to 3.3 ohms.

I'll probably skip this part. From what I hear it seems mostly useful if you're into pain or need to temporarily increase the level - which it seems could equally well be done by just turning the volume knobs(?)

For those who have and use "boost", I'd find it interesting to hear when and how you use it.

I would recommend a high-pass filter (blocks low frequencies) with a 35v (minimum) bi-polar capacitor between 100uf and 330uf. These are the values I've tried, Others could work. I added these capacitors and it felt a lot better for pleasure. It goes before the transformer. You could add a SPST toggle switch that bypasses the capacitor by bridging around it if you want more pain.

Would you say the higher capacitor value yields less pain or the opposite?
Can I just pick one, 100 or 330 without any further calculations or do I need to do some calculations?
If not, could this this one work?

Is the placement ok at C3, C4?

Screenshot_20221209_123751.png (24.24 KiB) Viewed 3043 times

[JakofClubs]

Would you say the higher capacitor value yields less pain or the opposite?
Can I just pick one, 100 or 330 without any further calculations or do I need to do some calculations?
If not, could this this one work?

Is the placement ok at C3, C4?

I believe most any capacitor value would block DC current. The higher the value, the lower the cutoff frequency, the more "pain" it lets through. I think 330uf is a good value to start with, but the effective cutoff frequency depends on the overall circuit resistance. My last box switches between 100, 220 and 330 uf. The 330 feels a bit more intense.

The capacitors need to be on one side ("positive" or "negative"), not between the two.
I believe the visaton-5394 would work. (English link https://www.conrad.com/p/visaton-5394-s ... 0-f-336718 )

This chart is for speakers but it demonstrates that as the capacitance value ( C ) goes up, the cutoff frequency goes down and that the impedance effects the cutoff frequency.

tableofcrossovercomponentvalues.gif (8.54 KiB) Viewed 3037 times

[fl0w]

The 330 feels a bit more intense.

But without would be more intense then? Guess that's a good starting point.

The capacitors need to be on one side ("positive" or "negative"), not between the two.

Sorry if I'm being dense here but wdym by on one side and not between +/-?
If I'm not misunderstanding you I thought that was what I had in my drawing?
To isolate the issue

Untitled.png (7.23 KiB) Viewed 3032 times

edit: Looking at this drawing I guess it could be said the capacitor is between positive and negative... So what does on one side mean here..?

[edger477]

edit: Looking at this drawing I guess it could be said the capacitor is between positive and negative... So what does on one side mean here..?

Do not put capacitor between positive and negative. How you drawn it is fine. Capacitor lets AC signal through, and stops DC. So it you put it between + and - you are short-circuiting all of the frequencies above 100-300 (very possibly blowing up the capacitor).

[fl0w]

Do not put capacitor between positive and negative. How you drawn it is fine. Capacitor lets AC signal through, and stops DC. So it you put it between + and - you are short-circuiting all of the frequencies above 100-300 (very possibly blowing up the capacitor).

Thanks for clarifying. That's what I thought I had done, i.e. not in parallel with the amp or transformer.

About having isolated channels, is it important (also?) that the AMP has isolated channels internally? And how can we verify that?